Display omitted
•Novel bimetallic Co/Ni phosphates were fabricated by two different synthetic approaches.•The as-prepared materials were studied in terms of different physicochemical tools.•The ...performance of CoNiP-R and CoNiP-S as electrode materials for UEO was evaluated.•The analyses affirm the high performance of the urea electrooxidation over CoNiP-S if it was compared with the CoNiP-R electrode.•This report presents novel cheap bimetallic phosphates towards the simple design of electrodes in UFCs.
Novel bimetallic Co/Ni phosphates were introduced in this work by two different synthetic strategies; reflux (CoNiP-R) and sol–gel (CoNiP-S) methods and evaluated as cheap electrodes for electrooxidation of urea (UEO) in alkaline medium (KOH medium). The as-prepared CoNiP-R and CoNiP-S materials were studied in terms of different physicochemical tools including Field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), transmission Electron Microscopy (TEM), dynamic light scattering (DLS), X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR) and Brunauer, Emmett and Teller (BET) surface area to understand what the effect of the synthetic method on the morphology, crystallinity, and surface area is. These investigations indicate the successful synthesis of smaller particles with higher surface area by sol–gel methodology if compared with the reflux method. The performance of CoNiP-R and CoNiP-S as electrode materials for UEO was evaluated through cyclic voltammetry (CV) at diverse urea contents and various sweep rates in addition to electrochemical impedance spectroscopy (EIS) and chronoamperometric (CA) methods. The synthesized CoNiP-S showed an enhanced UEO if compared with CoNiP-R at various urea doses up to 1.0 mol/l. Besides, the improvement of the obtained charge transfer resistance and current density indicates the increase of electrons generated from UEO.
Platinum is potentially employed as a catalyst in direct ethanol fuel cells (DEFCs). However, its scarcity and susceptibility to carbon monoxide poisoning give rise to novel challenges necessitating ...resolution. Transition metals such as nickel and cobalt are regarded as highly auspicious catalysts for DEFCs due to their perceived potential to reduce the expenditure associated with the synthesis procedure. In the present investigation, the synthesis of a cobalt-nickel (CoNi) catalyst with bimetallic properties was effectively accomplished through the electrodeposition technique utilizing the stimulator mode. Subsequently, an evaluation was conducted to assess the catalyst's proficiency in ethanol electrooxidation. The CoNi samples underwent comprehensive characterization through the utilization of various analytical techniques, namely X-ray diffraction (XRD), scanning electron microscopy (SEM), elemental dispersive X-ray analysis, and electrochemical impedance spectroscopy (EIS). The XRD analysis confirmed the formation of CoNi, while the SEM characterization demonstrated that the CoNi samples exhibited a homogeneous morphological feature. The impedance measured by the EIS technique displayed a resistance to charge transfer value of 21.21 kΩ, while the solution resistance value amounted to 66.67 kΩ. The catalytic efficiency of the specimens in ethanol electrooxidation was evaluated using the cyclic voltammetry technique, resulting in a peak current density of 3.14 mA/cm2 proving the potential of bimetallic CoNi to be a low-cost catalyst for ethanol electrooxidation process.
The electrooxidation of urea continues to attract considerable interest as an alternative to the oxygen evolution reaction (OER) as the anodic reaction in the electrochemical generation of hydrogen ...due to the lower potential required to drive the reaction and the abundance of urea available in waste streams. Herein, we investigate the effect of Sr substitution in a series of La2–x Sr x NiO4+δ Ruddlesden–Popper catalysts on the electrooxidations of urea, methanol, and ethanol and conclude that activities toward the urea oxidation reaction increase with increasing Ni oxidation state. The 75% Sr-substituted La0.5Sr1.5NiO4+δ catalyst exhibits a mass activity of 588 mA mgox –1 and 7.85 A mg–1 cmox –2 for the electrooxidation of urea in 1 M KOH containing 0.33 M urea, demonstrating the potential applications of Ni-based Ruddlesden–Popper materials for direct urea fuel cells and low-cost hydrogen production. Additionally, we find the same correlations between Ni oxidation state and activities for the electrooxidations of methanol and ethanol, as well as identify processes that result in catalyst deactivation for all three oxidations. This demonstration of how systematically increasing Ni – O bond covalency by raising the formal oxidation state of Ni above +3 serves to increase catalyst activity for these reactions will act as a governing principle for the rational design of catalysts for the electrooxidation of urea and other small molecules going forward.
Pd-based materials are promising electrocatalysts for the formic acid oxidation reaction (FAOR) but suffer from poor durability due to the poisoning of adsorbed carbon monoxide species (COads). In ...this work, PdBi ordered intermetallic (O-PdBi) nanoparticles were prepared in an effort to mitigate the formation of adsorbed species like COads through isolating the Pd atoms. The enhanced antipoisoning capability of O-PdBi, relative to Pd, gave rise to superior activity and stability during FAOR. Differential electrochemical mass spectrometry (DEMS) and CO stripping results indicated that COads could be removed more easily on O-PdBi compared with that on Pd. In situ attenuated total reflection-infrared spectroscopy showed that the formation of COads on O-PdBi was effectively suppressed, while both the hollow and bridged COads were detected on Pd with continuous Pd sites. In addition to the higher content of Bi atoms on the Pd-Bi surface, the ordered atomic distribution has played an important role in this effect. This work demonstrates the superiority of ordered intermetallic Pd-based nanocatalysts and provides guidance for promoting stability in FAOR by precluding the formation of COads.
Copper oxide-based materials show promising activity in biomass electrooxidation. However, systematic study of active sites evolution under electrochemical condition was rarely studied. In this work, ...we report copper oxide undergoes potential-dependent structure evolution with successive formation of Cu(OH)2 and CuOOH, which exhibit distinct activities in electrocatalytic glucose oxidation.
Display omitted
Electrocatalytic oxidation of renewable biomass (such as glucose) into high-value-added chemicals provides an effective approach to achieving carbon neutrality. CuO-derived materials are among the most promising electrocatalysts for biomass electrooxidation, but the identification of their active sites under electrochemical conditions remains elusive. Herein, we report a potential-dependent structure evolution over CuO in the glucose oxidation reaction (GOR). Through systematic electrochemical and spectroscopic characterizations, we unveil that CuO undergoes Cu2+/Cu+ and Cu3+/Cu2+ redox processes at increased potentials with successive generation of Cu(OH)2 and CuOOH as the active phases. In addition, these two structures have distinct activities in the GOR, with Cu(OH)2 being favorable for aldehyde oxidation, and CuOOH showed faster kinetics in carbon–carbon cleavage and alcohol/aldehyde oxidation. This work deepens our understanding of the dynamic reconstruction of Cu-based catalysts under electrochemical conditions and may guide rational material design for biomass valorization.
Electrocatalytic nitrogen oxidation to nitrate is a promising alternative to the conventional nitrate synthesis industry, which is accompanied by huge energy consumption and greenhouse gas emission. ...However, breaking the NN triple bond (941 kJ·mol–1) in nitrogen is still challenging, and thus, the development of efficient electrocatalysts with established reaction pathways is highly required. Herein, a series of Ru-doped Pd materials are prepared, and the optimized Pd0.9Ru0.1 sample exhibits superior performance for electrocatalytic nitrogen oxidation into nitrate, greatly outperforming pure Pd and Ru samples. The 15N isotope-labeling studies and other characterizations results indicate that the produced nitrate originates from N2 electrooxidation. Electrochemical in situ Raman spectra reveal the formed Pd0.9Ru0.1O2 on the surface serves as the active species. Electrochemical in situ Fourier transform infrared spectroscopy and online differential electrochemical mass spectrometry experimentally unveil the reaction pathway of nitrogen electrooxidation on Pd0.9Ru0.1O2. The combined results of experiments and theoretical simulations reveal Ru doping not only promotes the formation of more active species but also changes the potential-limiting step with a lower energy barrier.
Ultrathin metal–organic framework (MOF) nanosheets (NSs) offer potential for many applications, but the synthetic strategies are largely limited to top‐down, low‐yield exfoliation methods. Herein, ...Ni–M–MOF (M=Fe, Al, Co, Mn, Zn, and Cd) NSs are reported with a thickness of only several atomic layers, prepared by a large‐scale, bottom‐up solvothermal method. The solvent mixture of N,N‐dimethylacetamide and water plays key role in controlling the formation of these two‐dimensional MOF NSs. The MOF NSs can be directly used as efficient electrocatalysts for the oxygen evolution reaction, in which the Ni–Fe–MOF NSs deliver a current density of 10 mA cm−2 at a low overpotential of 221 mV with a small Tafel slope of 56.0 mV dec−1, and exhibit excellent stability for at least 20 h without obvious activity decay. Density functional theory calculations on the energy barriers for OER occurring at different metal sites confirm that Fe is the active site for OER at Ni–Fe–MOF NSs.
Ultrathin, binary MOF nanosheets (NSs) have been successfully prepared for the first time and directly used as efficient oxygen evolution reaction (OER) catalysts. The binary MOF NSs exhibit a highly composition‐dependent OER activity. The optimized Ni–Fe–MOF NSs are highly active and stable towards the OER.
In this work, PtAu nanoparticles were successfully synthesized using the electrodeposition technique. The nanoparticles obtained were irregularly spherical in shape and in the size range of 20-200 ...nm. X-ray diffraction (XRD) confirmed that the formed PtAu nanoparticles were alloys, because they showed a peak of 2θ in the region between Pt and Au metals, namely at 2θ 39.15˚ and 45.53˚. The cyclic voltammetry (CV) test showed that the PtAu catalyst has an ethanol electrooxidation activity of 22.9 mA/cm2, 11 times higher than the Pt catalyst previously synthesized using the same technique and conditions. In addition, at 300–1000 cycles the ethanol electrooxidation performance is fairly constant, indicating that this catalyst is quite stable. Interestingly alloying Pt with Au also increases the poisoning resistance of the catalyst from CO or other intermediate species. Thus, the use of PtAu catalysts can effectively increase catalytic activity, maintain stability of the catalyst, and reduce the possibility of poisoning by intermediate species.
α-Keto acids have been extensively employed as key starting materials in the synthesis of value-added chemicals. This review covers the recent breakthroughs achieved in the electrochemical ...transformations of α-keto acids.
Display omitted
As a kind of environmentally benign reagents, α-keto acids have been extensively employed as key starting materials in organic synthesis. Organic electrosynthesis has the advantages of reducing byproduct generation, improving the cost-efficiency of synthetic processes, and accessing reactive intermediates under mild conditions. Inspired by the merits of organic electrosynthesis, α-keto acids have shown many synthetic applications in electrochemical acylation, cyclization, and reductive amination reactions with improved efficiencies and selectivities. This review covers the recent breakthroughs achieved in the electrochemical transformations of α-keto acids, aimed at highlighting these electrochemical reactions’ features and mechanistic rationalisations. Meanwhile, the practicalities and limitations of these transformations are also presented where possible.
The study of metallic multilayers (MM) has presented interesting highlights to understand electrocatalytic properties for organic molecules oxidation. This work reports the preparation and ...characterization of MM using rhodium or ruthenium as an intermediate layer, Ptpc/Rh/Pt and Ptpc/Ru/Pt, aiming to evaluate the electrocatalytic activity toward methanol and ethanol oxidation in acid medium. For methanol electro-oxidation, the evaluated MM presented higher current density than Ptpc, especially Ptpc/Rh2/Pt1 and Ptpc/Ru5/Pt2, where the increase in peak current density was 283% and 422% compared to Ptpc. By in situ infrared spectroscopy (FTIR in situ), it was observed that in MM the CO2 formation from methanol oxidation occurred in lower potentials compared to Ptpc. In the ethanol oxidation, Ptpc/Rh2/Pt1 and Ptpc/Ru5/Pt2 increase in peak current density 32% and 67% compared to Ptpc, respectively. The bands referring to the acetaldehyde, acetic acid and CO2 were observed first to MM than for Ptpc. The better electroactivity of the metallic multilayers in the electro-oxidation of alcohols could be explained by the changes in the electronic interaction between the exposed platinum surface and the rhodium or ruthenium intermediate layer, which facilitated the oxidation of intermediates at lower potentials, and thus, increasing of the electrocatalytic activity of these materials.
•Metallic multilayers of Ru/Pt and Rh/Pt were evaluated toward MOR and EOR.•Ptpc/Rh2/Pt1 and Ptpc/Ru5/Pt2 showed an increase in current density compared to Ptpc.•Acetaldehyde, acetic acid and CO2 were observed first to MM than for Ptpc.•Electronic interaction between the Pt and Rh or Ru layer contributed to an activity increasing.
